Electronic article surveillance systems have been used for many years as a means of deterring retail shoplifting in clothing stores, electronic stores, and a myriad of other retail establishments. Generally speaking, an EAS system will begin with a tag, consisting of a durable and reliable, yet small, sensor tag which is affixed to the article to be detected in such a way that it cannot be easily removed by a customer in the store. Usually, the system depends upon the feature that the attachment mechanism is constructed such that it can only be removed by the use of a specialized tool which is only in the possession of the authorized store personnel at the checkout register or exit port for the establishment. In the event that an EAS tag is not removed from a protected article prior to exiting the store, an alarm or other signal is activated.
In many commercially available EAS systems, one or more antennas are placed at the exits and entrances to the retail location. These antennas set up zones, sometimes referred to as interrogation zones, in which an EAS tag (or marker) may be sensed. At least one antenna serves the function of sending out what is called an interrogation signal. The markers on the merchandise are affected by this signal and will respond with a signal of their own. Either the same antenna that sends out the interrogation signal or other additional antennas can sense the signals from the markers. The most effective way to do this is by stopping the broadcast of the interrogation signal to listen for the signals emanating from the markers. If a marker is sensed within the zone created by the antennas, it is presumed that an article is being removed without purchase, and alarms are set off. These alarms may be audible alarms for general broadcast or the alarms may be silent alarms in the form of a light at a check-out counter or security station, etc. Additionally, some EAS tags have onboard audible alarm generators and can generate audible alarms by themselves. These tags may produce this audible alarm when onboard logic elements determine that the tag is being removed from the store, or when the larger EAS system communicates to the tag to alarm. The onboard logic elements and the larger EAS system may also cause the tag to cease to alarm under certain situations.
An assortment of attachment mechanisms are available in the prior art. One of the more common and more successful attachment mechanisms is an EAS tag consisting of a tack which is used to physically pin the protected article to the EAS tag base. The tag base is usually constructed of a hard and durable plastic and is generally in the neighborhood of three inches long. The tag serves as a housing for an electronic signal generation means secured within the housing. The housing is designed to be resistant to tampering. A cap on the tack keeps the tag attached to the article.
Another common and successful method of attaching tags, or transponders, is a lanyard. One end of the lanyard is fixed in the transponder and the other end is capable of being inserted into an aperture in the transponder where it can be retained by the transponder. The lanyard can pass through an aperture on the article to be protected or may be placed around an article in a position where it cannot be simply slid off the article. The lanyard is typically constructed of material that is very difficult to break or cut, but yet, is easy to bend into place. A variation on lanyard tags passes the unfixed end of the lanyard through the body of its tag to form a loop which may be adjusted onto an object by pulling the unfixed end. A clutch in the body prevents the lanyard loop from being enlarged unless the clutch is release by an authorized person. Some tags may form more than one loop.
A common device for releasably retaining both tack shafts and lanyards is a ball clutch mechanism. The ball clutch mechanism may be constructed to release the retained item after application of a magnetic force to the tag. Other clips and clamps may also be used. Other types of tags may employ vials of ink, which may break if the tag is physically bent, thereby destroying the benefit of the theft attempt.
While tack, lanyard, and other types of tags have found wide use in protecting objects, they must remain attached to a given object to protect it. A common manner of defeating an EAS tag is to forcibly remove the tag from the object being protected. A countermeasure employed with some EAS tags is the introduction of a switch which has its state changed and arms the tag when a tag is attached to an object to be protected. For example, in tags employing a tack, a switch is positioned on the tag at a location beneath the head of the tack. When the tack is inserted through an object, the object and the head of the tack bear upon the switch and change its state. Depending on the mechanism being used to attach the tag to an object, a switch can be positioned to have its state changed when the tag is attached to an object.
Associated devices may communicate with electronics within the EAS tag to add an additional step to the tag arming process. When the tag is attached to an object and the state of the switch changed, this change of state functions as confirmation that the tag is attached, and an authorized person can use an associated device to wirelessly communicate with the tag to complete the tag installation and arming process. Once armed, if a tag is forcibly removed, the switch's state again changes, and the electronics of the EAS tag determine that an alarm condition exists. The EAS tag can sound an audible alarm with an onboard audible alarm generator or wirelessly communicate an alarm to other elements of the EAS system.
While both tack attached tags and lanyard attached tags have achieved wide acceptance in the field, they have limitations as well. The tacks of the tack attached tags must pierce the article to be monitored. This is not always desirable or even possible. Lanyards may be cut. There is a need for additional methods of releasably attaching an EAS tag to an object to be monitored.